Windshield wiper control

ABSTRACT

An electric control device controlling a wiper motor to operate windshield wiper blades intermittently with a dwell period between successive wiping cycles. The wiper motor current is carried by relay contacts and a solid state timing circuit controls the energization of the relay coil.

UIlltBd States Patent [191 [1 11 3,728,603

Kearns Apr. 17, 1973 [54] WINDSHIELD WIPER CONTROL 3,333,174 7/1967Moller et al. ..318/443 3,3 9, 8 19 [76] lnventor: Robert W. Kearns,20524 Ruther- 3 123 l 67 master 318/443 d A 4 for venue Detroit Mich8235' Primary ExaminerJ. D. Miller Filedi 1970 Assistant Examiner-RobertJ. Hickey 2 1 App] 4 451 Attorney-Lane, Aitken, Dunner & Ziems RelatedUS. Application Data [62] Division of Ser. No. 815,060, April 10, 1969,Pat. [57] ABSTRACT 7 An electric control device controlling a wlpermotor [52] US Cl "318/443 3 l 8/DIG 2 15/125012 to operate windshieldwiper blades intermittently with [51] Int. Cl. ..B60s 1/08 a PeriodSuccessive wiping cycles- The [58] Field of Search ..318/443; 15/250.12Wiper motor current is carried y relay contacts and a solid state timingcircuit controls the energization of [56] References Cited the relaycoil.

UNITED STATES PATENTS Yonkers, Jr, ..3l7/l13 X 1 Claim, 4 DrawingFigures PATENTEU APR 1 11m SHEEI 1 BF 2 DASHBOARD INVENTOR ROBERT wKEARNS PATENTEU APR 1 71m.

sum 2 [JP 2 PAR OPEN AT OFF I O 2 B Q K RUN r? I82) PAR-2 ROBERT W.KEARNS WINDSHIELD WIPER CONTROL CROSS-REFERENCE TO RELATED APPLICATIONThis is a divisional application based on applicant's copendingapplication Ser. No. 815,060 filed Apr. 10, 1969, issued May 25,1971, asU.S. Pat. No. 3,581,178.

BACKGROUND OF THE INVENTION In my US. Pat. No. 3,351,836 issued on Nov.7, 1967, a transistorized control device is disclosed for controllingthe electric motor of an automotive windshield wiper motor unit. Thecontrol device can be actuated by the driver to off, continuous andintermittent positions. In the continuous position the wiper bladesoperate continuously through repeating wiping cycles. In the offposition they complete the wiping cycle in progress and stop at the parkposition. In the intermittent position the wiper blades operate for acomplete wiping cycle and stop at the end of each wiping cycle for adwell period.

In the control device of my patent the emitter-collector of a transistoris connected in series with the electric motor to control theenergization and deenergization of the motor. A capacitive timingcircuit cooperates with the base circuit of the transistor to bias itoff for the dwell periods at the end of each wiping cycle in theintermittent mode of operation. An electrodynamic brake resistor isconnected across the motor to electrodynamically brake the motor at thebeginning of each dwell period. At the end of each dwell period, thebrake resistor remains connected across the motor until the motorrotates through a small angle to activate a motor responsive switch todisconnect the brake resistor. This reduces the starting torque when themotor is energized by the transistor to begin the next wiping cycle.

SUMMARY OF THE INVENTION The present invention provides a wiper controldevice having a relay in place of the aforementioned transistor forcontrolling the energization of the wiper motor. The relay contacts alsoconnect an electrodynamic brake across the motor when the motor isdeactivated. The transistor and capacitive timing means of my patent areemployed in the intermittent mode for controlling the energization anddeenergization of the relay coil so that the transistor carries the muchlower current of the relay coil. When the relay coil is energized tostart the next wiping cycle, the relay contacts disconnect theelectrodynamic brake and connect the motor to the battery to producefull power at the very beginning of each wiping cycle.

The preferred embodiment employs a three-brush, permanent magnet motorhaving high and low speed brushes. When the low speed brush is used, thecontrol device operates the motor in the intermittent mode of operationwith electrodynamic braking when the motor is deenergized. When the highspeed brush is used, the wiper blades cycle continuously at high speed,and the relay contacts are maintained in a position such that theelectrodynamic brake is disengaged and does not interfere with the highspeed continuous operation.

The preferred embodiment is particularly well suited for the aftermarket, rather than the OEM market, that is, for installation on carsafter delivery from the factory, rather than for installation by themanufacturer on the production line. All of the electrical components ofthe control device are contained in a small housing or cover mounted onthe bottom of the relay can to provide a simple, economic package thatcan be mounted on the dashboard and spliced into the wires connectingthe existing wiper control switch to the wiper motor without making anychanges in the control switch and motor.

The objects and features of novelty of the present invention will bepointed out specifically or will otherwise become apparent whenreferring, for a better understanding of the invention, to the followingdescrip tion taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of acontrol device em- DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring toFIG. 1, a control device 10 is illustrated which embodies features ofthe invention. It controls the operation of a conventional three-brushpermanent magnet motor 12 having a low speed brush 14, a high speedbrush 16 and a third brush 18 connected directly to ground. As is wellknown, when the battery potential 3+ is applied to the high speed brush16, fewer of the armature windings are energized between the high speedbrush and the third brush is as compared to the windings energized whenthe potential 8+ is applied between the low speed brush 14 and the brush18. Therefore, in the high speed position the motor operates at a higherspeed and lower torque than in the low speed position.

A conventional control switch 20 is provided which can be mounted on thedashboard of the automotive vehicle in position to be operated by thedriver. The control switch has moveable contacts 22 and 24 mechanicallycoupled together for actuation by a single knob (not shown). In theposition illustrated, the moveable contacts 22 and 24 engage theirrespective park terminals P and are moveable into engagement with lowspeed terminals L and high speed terminals H. The high speed terminal Hassociated with the moveable contact 22 is connected through a circuitbreaker 26 to a terminal 28 which is connected to the positive terminalof the vehicle battery to apply a potential 8+ to the terminal 28. Thelow speed terminal L associated with the moveable contact 24 also isconnected to the terminal 28.

A relay 30 is provided with a relay coil 32 for actuating a moveablecontact 34 between a fixed contact 36 connected to ground and a fixedcontact 38 connected to the moveable contact 24 of the control switch.The moveable contact 34 is normally biased into engage ment with thefixed contact 36 by a spring 40 when the relay coil 32 is deenergized asshown in FIG. 1.

One end of the relay coil 32 is connected to a wire 44 having one endthereof connected to 3+ through the terminal 28. The other end of thewire 44 is connected to a fixed contact 46 associated with a moveablecontact 48 of a motor responsive switch having another fixed contact 50connected to ground. The other end of the relay coil 32 is connected toground through the emitter-collector circuits of three transistors 52,54 and 56.

One end of a resistor 58 is connected to the base of the transistor 56and the other end is connected to the negative side of a capacitor 60.The positive side of the capacitor is connected to a wire 62 having oneend connected to the moveable contact 48 and the other end connected tothe park terminal P associated with the moveable contact 24 of thecontrol switch 20. One end of a resistor 64 is connected to the juncturebetween the resistor 58 and the transistor 56, and the other end isconnected to a resistor 66 of a potentiometer having a wiper arm 68connected to a terminal 70 which is connected to the potential B+. Adiode 71 is connected between a wire 42 and the juncture between theresistor 64 and the potentiometer resistor 66. The wire 42 connects thehigh speed brush 16 to the moveable contact 22. A resistor 72 isconnected in parallel with the resistor 58 and the capacitor 60.

By way of example, the resistors may have the following values: 2.7K forthe resistor 58, 1.5K for the resistor 64, l megohm for thepotentiometer resistor 66 and 390K for the resistor 72. The capacitormay have a value of lmfd at WVDC.

The moveable contact 48 of the motor responsive switch is actuated bythe motor 12 so that is cycles once each wiping cycle of the wiperblades. The moveable contact 48 engages the fixed contact 46(hereinafter referred to as the run contact) during a wiping cycle andengages the fixed contact 50 (hereinafter referred to as the parkcontact) while the wiper blades move through a small angle near the endof each wiping cycle.

When the operator turns the control switch 20 to the low speedposition'the moveable contact 24 engages the low speed terminal L and isconnected to 8+ through the terminal 28. The wiper arm 68 is then movedfrom a position out of engagement with the upper end of thepotentiometer resistor 66 into engage ment with the upper end so as toapply 3+ to the potentiometer resistor through the terminal 70. Thismakes the base of the transistor 56 positive and turns the transistorson to energize the relay coil 32 and move the moveable contact 34 intoengagement with the fixed contact 38. Since the fixed contact 38 isconnected to B+ through the moveable contact 24 of the control switch20, and since the moveable contact 34 is connected directly to the lowspeed brush 14 of the motor, the motor is energized at low speed and thewiper blades begin a wiping cycle.

After a few degrees of movement the moveable contact 48 automaticallymoves into engagement with the run contact 46 of the motor responsiveswitch, and remains in this position until the wiper blades complete awiping cycle. Thus, during a wiping cycle while the moveable contact 48engages the run contact 46, the

right side of the capacitor 60 is connected to B+ through the terminal28 and the capacitor 60 charges as described in my aforementionedpatent. At the end of the wiping cycle, the moveable contact 48 is movedinto engagement with the park contact 50 to connect the right side ofthe capacitor to ground. Since the charge across the capacitor cannotchange instantane ously, this drops the potential on the negative sideof the capacitor by the amount of the charge on the capacitor. Thisapplies a negative potential to the base of the transistor 56 to biasthe transistors off, deenergize the relay coil 32 and shift the moveablerelay contact 34 into engagement with the fixed contact 36 to connectthe low speed brush 14 to ground. Since the third brush 18 also isconnected to ground, the motor is electrodynamically braked to a stop.

The transistors remain off for a time interval determined by the time ittakes for the capacitor 60 to discharge through the RC timing circuitincluding the resistors 58 and 64, and the potentiometer 60. Since thepotentiometer resistor 66 is large in comparison to the other tworesistors, it in effect controls the discharge time of the capacitor.When the capacitor discharges sufficiently so that the base of thetransistor 56 again becomes slightly positive, the transistors arebiased on to begin the next wiping cycle. Specifically, the relay 32 isenergized by the transistor, the moveable contact 34 is moved intoengagement with the fixed contact 38 to connect the low speed brush 14to B+, and the motor 12 is energized to start the next wiping cycle. Itis important to note, however, that before the motor is energized tostart the wiping cycle, the ground connection at the fixed relay contact36 is broken to disconnect the electrodynamic brake across the motor 12so that the motor starts the wiping cycle with the full torque at lowspeed.

The length of time of the swell period can be varied by changing theposition of the wiper arm 68 to vary the portion of the potentiometerresistor 66 through which the capacitor 60 discharges. As the wiper arm68 moves from the open end of the resistor toward the end thereofconnected to the resistor 64, the resistance decreases and the dwellperiod decreases. During this movement a point will be reached near thelower end of the potentiometer resistor 66 where a positive potential isapplied continuously to the base of the transistor 56 through theterminal regardless of the charging and discharging of the capacitor 60.Therefor, at this point, the relay coil 32 will remain energizedcontinuously and the wiper blades will operate continuously at low speedwithout dwell periods and without electrodynamic braking.

When the control switch is moved to the high speed position, themoveable contact 22 engages the high speed terminal H and is connectedto 8+ through the terminal 28. This applies B+ directly to the highspeed brush 16 through the wire 42 and operates the motor 12 at highspeeds. At the same time the juncture between the resistor 64 and thepotentiometer resistor 66 is connected to 8+ through the diode 70 sothat the transistors remain biased on continuously during high speedoperation. This maintains the relay coil 32 energized continuouslywhich, in turn, maintains the moveable contact 34 in engagement with thefixed contact 38 which is not connected to any potential. Maintainingthe moveable relay contact 34 in this position prevents theelectrodynamic brake being applied to the motor while it is in highspeed operation.

When the control switch 20 is moved to the park position as illustrated,the moveable contact 24 is connected to the moveable contact 48 of themotor responsive switch through the wire 62. At the same time, the wiperarm 68 is disconnected from the upper end of the potentiometer resistor66 to remove the B+ potential applied through the terminal 70. If themove- .able contact 48 of the motor responsive switch is in the positionillustrated wherein it engages the park contact 50, the transistors willbe biased off and the relay coil 32 will be deenergized to terminate thewiping operation with the wiper bladesin the park position. If themoveable contact 48 is engaging the run contact 46, the wiping cycle inprogress will continue until the end of the cycle at which point themoveable contact moves into engagement with the park contact 50 to applythe electrodynamic brake and terminate further wiping operations.

In the preferred embodiment just described, the

wiper arm 68 is operated by a separate control knob 80 mounted on apackage 82, as illustrated in FIG. 2. The package 82 comprises aconventional relay 84 having an insulated base 86 and a housing 88mounted on the base to enclose the relay components. The latter includesthe relay coil 32 and contacts 34-38. The remaining electroniccomponents of the control device contained in a housing 90 mounted onthe underside of the insulated base 86. These include the transistors52-56, the diode 71, the capacitor 60, and all of the resistorsillustrated in FIG. 1.

Three terminals 92-96 are mounted on and project from the underside ofthe base 86 for making the external connections to the components withinthe cover 90. Specifically, the terminal 92 is used to make the groundconnection for the emitters of the transistors, the terminal 94 is usedto connect the diode 71 to the wire 42 and the terminal 96 is used toconnect the positive side of the capacitor to the wire 62 of FIG. 1.Four terminals 98-104 are mounted on and project from the upper side ofthe insulated base 86 for making the nextconnections to the relay coiland contacts. Specifically, the terminal 98 is used to connect thestationary contact 36 to ground, the terminal 100 is used to connect thestationary contact 38 to the moveable contact 24, the terminal 102 isused to connect the moveable contact 84 to the low speed brush 14 andthe terminal 104 is used to connect the relay coil to the wire 44. Theconnection between the relay coil 32 and the transistors 52-56 is madeinternally and, therefore, not shown in FIG. 2.

A mounting or face plate 106 is secured to the cover 90. It has a flange108 on one edge thereof for mounting the package 82 on the underside ofthe dashboard of an automotive vehicle, preferably immediately below thewindshield wiper control switch 20 so that the control knob 80 is in aconvenient position to be adjusted by the driver to control the positionof the wiper arm 68.

The knob 80 is provided with a pointer 110 which cooperates withsuitable indicia on the exposed face of the plate 106 to indicate theposition of the wiper arm 68. For example, the indicia could indicatethe following positions of the knob 80; OFF, MAXIMUM DWELL, MINIMUMDWELL and LOW SPEED. In its extreme counterclockwise position thepointer 110 would point to OFF and, in this position, the wiper arm 68would be disconnected from the open end of the potentiometer resistor66. When the knob is moved in a clockwise direction to the MAXIMUM DWELLposition, the wiper arm 68 would be connected to the end of thepotentiometer resistor 66. As the knob is moved from this position tothe MINIMUM DWELL position, the wiper arm 68 decreases the portion ofthe potentiometer resistance 66 through which the capacitor 60discharges. When the knob 80 is rotated to its extreme clockwiseposition with the pointer pointing to the LOW SPEED position, the wiperarm 68 would be at its lowermost position and remove all of thepotentiometer resistor 66 from the discharge path of the capacitor 60.

It is apparent that the control device of FIGS. 1 and 2 readily lendsitself to sale in the aftermarket. The control device would be marketedin the form of the package 82, and would have suitable wires connectedto the terminals 92-104 for making the necessary connections to theexisting wiper control switch and motor of the particular car for whichthe control device is designed. As mentioned previously, the controlswitch 20, the motor 12 (and the motor responsive switch actuatedthereby) and the connecting wires 42, 44 and 62 are those now being usedby one of the leading car manufacturers on some of its cars. Therefore,for these cars, the package 82 need only be mounted beneath thedashboard and the wires on the terminals 92-104 connected as shown inFIG. 1.

Referring to FIG. 3 a control device is shown which illustrates anotherembodiment of the invention for controlling the motor 12. As in theembodiment of FIG. 1 the motor 12 actuates the motor responsive switchhaving the moveable contact 48 and the run and park contacts 46 and 50.The park contact 50 is connected directly to ground and the run contact46 is connected to a terminal 122 which is connected to the positiveterminal of the battery.

The main difference between the control device 120 and the controldevice of FIG. 1 is that it employs two relays 122, and 124, and that itdoes not employ a control switch 20. Its entire operation is controlledby the position of the wiper arm 68. The transistors, resistors andcapacitor are the same as those of FIG. 1. However, the collector oftransistor 56 is connected to coil 126 of relay 124 through a resistor128. The other ends of each of the relay coils are connected to 8+through a terminal 132. The moveable contact 134 of the 'relay 122 isconnected to the low speed brush 14, the fixed contact 136 is connectedto ground and the fixed contact 138 is connected to a fixed contact 140of the relay 124. A moveable contact 142 is connected to 8+ through acircuit breaker 144 and a terminal 146. A fixed contact 148 of the relay124 is connected to the high speed brush 16 of the motor.

When the knob which controls the wiper arm 68, is in its OFF position,the motor 12 is deenergized, the wiper blades are in the park positionand the wiper arm 68 is disconnected from the open end of thepotentiometer resistor 66. When the knob is rotated to engage the wiperarm with the open end of the potentiometer resistor 66, the wiper bladesoperate in the intermittent mode of operation as previously describedwith a dwell period between successive wiping cycles. As before thelength of time of the dwell periods is determined by the rate at whichthe capacitor 60 discharges through the potentiometer resistor 66. Whenthe capacitor discharges sufficiently to bias the base of the transistor56 positive, all three transistors turn on to energize the relay coil130 to start the next wiping cycle. The relay coil 126 is not energized,despite the fact that the transistor 56 is biased on, because of theresistor 128 which controls the switching point and hysterisis of therelay 124. The value of the resistance 128 is about 22 ohms, and all ofthe other resistors have the same resistance values, the same as in theembodiment of FIG. 1.

When the relay coil 130 is energized, as just described, the moveablecontact 134 engages the fixed contact 138 to connect the low speed brush14 to 8+ through the contacts 140 and 142 of the relay 124. During thewiping cycle, the moveable contact 48 of the motor responsive switchengages the run contact 46 to charge the capacitor 60 as before. At theend of the wiping cycle, the moveable contact 48 engages the parkcontact 50 to stop the wiper blades for a dwell period by jumping thecharge on one side of the capacitor 60 to bias the transistors off aspreviously described.

When the wiper arm 68 is moved to decrease the potentiometer resistor 66in circuit with the capacitor 60, the length of the dwell periodsdecreases. As the potentiometer resistance is decreased, a first pointis reached where relay coil 130 remains energized continuously (withrelay coil 126 still deenergized) so that the wiper blades operatecontinuously at low speeds without dwell periods despite the chargingand discharging of the capacitor 60 during each wiping cycle.

When the potentiometer resistance 66 is decreased still further, asecond point is reached where the current passing through the relay coil126 is sufficient to energize the relay coil and move the moveablecontact 142 into engagement with the fixed contact 148. This connectsthe high speed brush 60 directly to B+ through the terminal 146 andbreaks the circuit to the low speed brush 14 so that the wiper bladesoperate continuously at high speed. Therefore, the first and secondpoints on the potentiometer resistor 66 as just described correspond tothe low and high speed positions, respectively.

The wiper arm 68 can be controlled by a single control knob similar tothe control knob 80 of FIG. 2, and the pointer of the control knob cancooperate with suitable indicia to indicate four different positions,OFF, MAXIMUM INTERMITTENT, LOW SPEED and HIGH SPEED continuouspositions. As in the case of FIG. 2 the relays and all the electroniccomponents can be contained in a single package suitable for the aftermarket. However, in this case, the wiper motor switch already on the carwould not be used, and the wiper blades would be controlled solely bythe knob which controls the position of the wiper arm 68.

When the wiper arm 68 is moved to the OFF position out of engagementwith the potentiometer resistor 66, the wiper blades complete the cyclein progress because 8+ is connected to the positive side of thecapacitor 60 through the run contact 46 and the moveable contact 48.When the wiper blades reach the park position the moveable contact 48engages the park contact 50 to bias the transistors off and terminatefurther wiping operations. As in the control device of FIG. 1, theparking operation is accomplished through the low speed brush 14.

If desired, the fixed contact 136 can be connected to ground through apredetermined brake resistance which is connected across the motor whenthe motor is deenergized. This electrodynamically brakes the motor witha braking force less than that when the brushes 14 and 18 are connectedto ground. This same resistance could be added to the control device 10of FIG. 1. By providing such a braking resistor, the safety skip featureof my aforementioned patent is introduced in the intermittent mode ofoperation so that when the moisture on the windshield changes, the dwellperiods are skipped automatically to provide continuous operation untilthe moisture decreases sufficiently to enable the dwell periods tocommence again automatically. The safety skip feature can be added tothe control device 10 of FIG. 1 by connecting the fixed contact 36 toground through the same type of brake resistance.

Referring to FIG. 4, a control device is illustrated which is moresuited for the OEM market because it employs a special wiper controlswitch 162 which can best be installed in the car by the carmanufacturer. The control switch 162 has a pair of moveable contacts 164and 166 connected together for actuation by a single control knob orlever (not shown). The moveable contact 164 is connected to ground andthe moveable contact 166 is connected to B+ potential through a circuitbreaker 168 and a terminal 170. An arcuate contact.172 is associatedwith the moveable contact 164 and connected directly to the brush 18 ofthe motor 12. An identical arcuate contact 174 is associated with themoveable contact 166 and connected directly to the upper end of therelay coil 32. A potentiometer resistor 176 is positioned within thearcuate contact 164 with one end thereof connected to a low speedterminal LO which, in turn, is connected to the juncture between thediode 70 and the resistor 64. A high speed terminal III is locatedbetween the low speed terminal and an OFF terminal which is engaged bythe moveable contact 166 in the OFF position, as illustrated in FIG. 4.A shorter arcuate contact 178 is positioned within the potentiometerresistor 176 and connected directly to the fixed relay contact 38. Asbefore, the fixed relay contact 36 is connected directly to ground.

To start the wiper blades the control switch 162 is moved by the driverto the high speed position wherein the moveable contact 164 engages thearcuate contact 172 and the moveable contact 166 engages the HIterminal. This connects the brush 18 to ground through the moveablecontact 164 and the high speed brush 16 to 8+ through the moveablecontact 166 and the terminal so that the wiper motor is energizedcontinuously at high speed. As in the embodiment of FIG. 1, thetransistors are biased on because of the positive potential applied tothe base of the transistor 56 through the diode 70, an therefore, therelay 32 remains energized to maintain the moveable contact 34 inengagement with the fixed contact 38 to prevent the electrodynamic breakfrom being applied during high speed operation.

When the control switch 162 is moved by the driver to the low speedposition, the moveable contact 166 engages the arcuate contact 178 andthe LO terminal. This breaks the circuit to the high speed brush 16 andconnects the resistor 64 to B+ through the wire 180, the moveablecontact 166 and the terminal 170. Therefore, the transistors are biasedon continuously to maintain the relay coil 32 energized continuously,and the moveable contact 34 engages the fixed contact 38 to connect thelow speed brush 16 to B+ through the arcuate contact 178, the moveablecontact 166 and the terminal 170. Consequently, the wiper blades operatecontinuously at low speed.

As the moveable contact 166 is rotated in a clockwise direction from theLO terminal, the portion of the potentiometer resistor 176 in serieswith the resistor 64 increases until a point is reached at which thetransistors are biased off for dwell periods at the end of each wipingcycle with the length of the dwell periods determined by the time ittakes for the capacitor 60 to discharge through the portion of thepotentiometer resistor 176 connected in the circuit. When the entirepotentiometer resistor 176 is connected in the circuit, the dwellperiods are at their maximum, as in the case of the control device ofFIG. 1.

When the control switch 162 is moved to the off position as illustratedin FIG. 4, the moveable contact 164 is disconnected from the arcuatecontact 172 to break the ground connection to the brush 18. The moveablecontact 166 engages the OFF terminal to connect a run contact 182 of areverse park switch 184 to B+ through the terminal 170. Assuming awiping cycle is in progress, when the control switch 162 is turned toOFF, the moveable contact 186 of the reverse park switch is inengagement with the run contact 182 to connect the brush 18 to 3+. Thelow speed brush 14 is connected to ground through the moveable relaycontact 34 and fixed relay contact 36, the relay coil 32 beingdeenergized as soon as the moveable contact 166 is disconnected from thearcuate contact 174 to remove B+ from the upper end of the relay coil32.

With the brush 18 at B+ and the low speed brush 14 at ground, the motor12 operates in reverse until the wiper blades reach the park position.At this point the moveable contact 186 of the reverse park switch movesto its park contact 188 to ground the brush 18. This electrodynamicallybreaks the motor 12 to a stop at the park position and terminatesfurther wiping cycles.

The reverse park switch 184 is a well known type of switch employed bycar manufacturers to provide a depressed park position, and therefore,will not be described in detail. It is sufficient to state that it isactu ated by the motor 12 only when the motor 12 is operattion, a lowspeed continuous position and then into intermittent operation withincreasing dwell periods as the knob or lever is moved further.

The control device also brings the reverse park switch 184 into play ina simple manner when the control switch 162 is returned to its offposition. As in the other embodiments, the wiper motor 12 is run at lowspeed during the parking operation to develop maximum torque. This isimportant, particularly when the wiper blades are moved off of the glassinto a slot along the bottom of the windshield in order to reach thedepressed park position as they are in many to todays cars. Moving thewiper blades off the glass into such a slot requires significantlygreater torque as compared to parking them on the glass.

I claim:

1. A control device for activating windshield wiper drive means fordriving wiper blades through repeating wiping cycles comprising relaymeans having first, second and third conditions, and control means foractivating said drive means when said relay means is in said firstcondition and deactivating said drive means when said relay means is insaid second condition, said control means including a variableresistance having a movable wiper arm, said control means cycling saidrelay means through said first and second conditions in a manner todrive said wiper blades through repeating wiping cycles with dwellperiods between successive wiping cycles, the length of time of saiddwell periods being determined by the value of said resistance, saidcontrol means operating said wiper blades continuously at a first speedwithout dwell periods between wiping cycles with said relay meansmaintained in said first condition when said resistance reaches a firstpredetermined value and continuously at a second speed with said relaymeans maintained in said third condition when the value of saidresistance reaches a second predetermined value, said control meansparking said wiper blades and terminating further wiping cycles whensaid wiper arm is disconnected from said variable resistance.

4* i I! i It

1. A control device for activating windshield wiper drive means fordriving wiper blades through repeating wiping cycles comprising relaymeans having first, second and third conditions, and control means foractivating said drive means when said relay means is in said firstcondition and deactivatinG said drive means when said relay means is insaid second condition, said control means including a variableresistance having a movable wiper arm, said control means cycling saidrelay means through said first and second conditions in a manner todrive said wiper blades through repeating wiping cycles with dwellperiods between successive wiping cycles, the length of time of saiddwell periods being determined by the value of said resistance, saidcontrol means operating said wiper blades continuously at a first speedwithout dwell periods between wiping cycles with said relay meansmaintained in said first condition when said resistance reaches a firstpredetermined value and continuously at a second speed with said relaymeans maintained in said third condition when the value of saidresistance reaches a second predetermined value, said control meansparking said wiper blades and terminating further wiping cycles whensaid wiper arm is disconnected from said variable resistance.